Increasingly stringent legislation governing permissible pollutant emissions from motor vehicles, in which internal combustion engines are disposed, requires pollutant emissions to be kept as low as possible during operation of the internal combustion engine. This can be achieved on the one hand by reducing the pollutant emissions resulting during combustion of the air/fuel mixture in the respective cylinder of the internal combustion engine.
On the other hand exhaust gas post-treatment systems are deployed in internal combustion engines to convert the pollutant emissions produced in the respective cylinders during the combustion process of the air/fuel mixture to harmless substances.
Catalytic converters are used for this purpose, which convert carbon monoxide, hydrocarbons and nitrogen oxides to harmless substances.
Both the specific influencing of the production of pollutant emissions during combustion and the conversion of the pollutant components by a catalytic converter with a high level of efficiency require very precise setting of the air/fuel ratio in the respective cylinder.
Known from the technical publication titled “Handbuch Verbrennungsmotor” (appearing in English as “Internal Combustion Engine Handbook”), edited by Richard van Basshuysen and Fred Schäfer, 2nd edition, published by Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, pages 559-561, is a linear lambda regulator with a linear lambda probe, which is disposed upstream of an exhaust gas catalytic converter, and a binary lambda probe, which is disposed downstream of the exhaust gas catalytic converter. A setpoint lambda value is filtered by means of a filter, taking into account the gas travel times and sensor response. The setpoint lambda value thus filtered is the controlled variable of a PIII2D lambda regulator, the manipulated variable of which is an injected quantity correction.
Also known from the technical publication titled “Handbuch Verbrennungsmotor” (appearing in English as “Internal Combustion Engine Handbook”), edited by Richard van Basshuysen and Fred Schäfer, 2nd edition, published by Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, pages 559-561, is a binary lambda regulator with a binary lambda probe, which is disposed upstream of the exhaust gas catalytic converter. The binary lambda regulator comprises a PI regulator, with the P and I components being stored in engine characteristic maps relating to engine speed and load. With binary lambda regulation the excitation of the catalytic converter, also referred to as lambda fluctuation, results implicitly from second point regulation. The amplitude of the lambda fluctuation is set at around three percent.
Special significance attaches to the lambda probe(s) in respect of lambda regulation. In this context it is necessary, for example due to statutory regulations, to monitor the lambda probe in an appropriate manner.